Known in the art for producing sulfonic acid ester derivatives represented by the above general formula (4) or (5) are the method comprising reacting the corresponding amino alcohol derivative with an organic sulfonyl halide in an organic solvent in the presence of an organic base, for example a tertiary amine such as triethylamine or an aromatic amine such as pyridine, or in such an organic base; and the method comprising reacting the corresponding amino alcohol derivative with an organic sulfonyl halide in an anhydrous organic solvent in the presence of a water-prohibiting base such as sodium hydride or sodium amide.
Specifically, there are known the method comprising reacting 1-benzyl-3-pyrrolidinol with methanesulfonyl chloride or toluenesulfonyl chloride in the presence of an organic base such as triethylamine or pyridine (JP-A-07-116138; J. Med. Chem., 35 (1992) 22, 4205-4213) and the method comprising reacting 1-benzyl-3-pyrrolidinol with toluenesulfonyl chloride in an anhydrous solvent such as benzene or tetrahydrofuran in the presence of a water-prohibiting base such as sodium hydride or sodium amide (JP-A-51-125286; Laid-open European Patent EP-0928787), among others.
However, these known production methods have the following problems, among others:    1) When an organic base such as a tertiary amine or an aromatic amine is used, the organic base is expensive. For isolating the sulfonic acid ester formed as an intermediate for the synthesis of fine chemicals such as medicinal compounds or agrochemicals, which are required to be of high quality, a high-level of purification for removal of the organic base, such as crystallization, distillation and/or column chromatography, is required (since the product sulfonic acid ester derivative itself is a kind of organic base, it is difficult to purify the same by such a simple technique as phase separation). The organic base is obtained as waste in an amount at least one equivalent relative to the product sulfonic acid ester derivatives.    2) When a water-prohibiting base, such as sodium hydride or sodium amide, is used, such water-prohibiting base itself is expensive. Such water-prohibiting base has a safe problem in handling in using it on a commercial scale.    3) In all the known methods, a high-level of purification, for example removal of the organic base by rectification, and/or dehydration, is required if the solvent is to be recovered and recycled. Such a purification process is economically difficult in many cases and the solvent is discharged as waste in increased amounts.
Thus, when evaluated as methods capable of reducing the load on the environment in the production of intermediates for high-quality fine chemicals such as medicinal compounds and agrochemicals on a commercial scale and in an economical manner, the prior art methods have problems.
In view of the state of the art as mentioned above, it is an object of the present invention to provide a method of economically producing the sulfonic acid ester derivatives represented by the general formula (4) or (5), which are intermediates for the synthesis of fine chemicals such as medicinal compounds or agrochemicals, which are required to be of high quality, in a simple and easy and safe manner while reducing the load on the environment.